In the oil and gas industry, seismic prospecting techniques are used to aid in the search for and evaluation of subterranean hydrocarbon reservoirs. A seismic prospecting operation consists of three stages: data acquisition, data processing, and data interpretation. The success of the operation depends on satisfactory completion of all three stages.
In the data acquisition stage, a seismic source is used to generate an acoustic signal that propagates into the earth and is at least partially reflected by subsurface seismic reflectors. The reflected signals are detected and recorded by an array of seismic receivers located at or near the surface of the earth, in an overlying body of water, or at known depths in boreholes.
During the data processing stage, the recorded seismic signals are refined and enhanced using a variety of procedures that depend on the nature of the geologic structure being investigated and on the characteristics of the raw data. In general, the purpose of the data processing stage is to produce an image of the subsurface from the recorded seismic data for use during the data interpretation stage.
The purpose of the data interpretation stage is to determine information about the subsurface geology of the earth from the processed seismic data. The results of the data interpretation stage may be used to determine the general geologic structure of a subsurface region, or to locate potential hydrocarbon reservoirs, or to guide the development of a discovered reservoir.
Due to the limited resolution of seismic data, the conclusions which can be made after the data interpretation stage are generally limited to broad descriptions of the size and overall shape of subsurface reservoirs. The descriptions may for example provide an indication of the total volume of hydrocarbons which might be retained in such reservoirs. However, present technology does not allow the analyst to accurately determine the detailed internal structure of the reservoir from seismic data. Even when an exploration well has been drilled, present technology does not allow an analyst to accurately characterize detailed reservoir structure in locations other than in the most immediate region of any such well.
A commercial hydrocarbon reservoir is generally a “composite” sedimentary body, composed of a large number of smaller “fundamental” sand bodies, many of which are too small to be separately distinguished in a seismic image. Reservoir continuity, the communication (or lack thereof) between adjacent sand bodies, is commonly a primary factor controlling hydrocarbon production efficiency and ultimate recovery. There is a need to predict detailed internal structure of subsurface reservoirs using seismic data and without having to drill many exploration and delineation wells. Such a capability would facilitate estimation of hydrocarbon volume in place and production rates early in the hydrocarbon exploration and development process. Accordingly, this invention satisfies that need.